2-Minute Neuroscience: Neuromuscular Junction Video Lecture | A-Z Guide to Neuroscience - Personal Learning

Welcome to 2 minute neuroscience, where I
simplistically explain neuroscience topics
in 2 minutes or less.
In this installment I will discuss the neuromuscular
junction.
The term neuromuscular junction refers to
the synapse between a motor neuron and a skeletal
muscle fiber.
Activity at the neuromuscular junction is
essential for the contraction of skeletal
muscle to occur, and even just to keep muscles
from atrophying.
It is also the site where synaptic transmission
was first studied and thus is the best understood
example of chemical signaling in the nervous
system.
When a motor neuron approaches a muscle, it
branches out into several extensions that
end in areas called synaptic boutons, which
can release neurotransmitters.
These synaptic boutons are situated over a
specialized region of muscle called the end-plate.
The synaptic boutons are separated from the
end plate by a space called the synaptic cleft.
The end-plate beneath each synaptic bouton
contains several deep indentations called
junctional folds.
These junctional folds contain high numbers
of ligand-gated ion channel receptors for
the neurotransmitter acetylcholine.
When an action potential travels down the
motor neuron, it causes the release of acetylcholine
into the synaptic cleft.
Acetylcholine binds to acetylcholine receptors
in the junctional folds of the muscle membrane,
which causes ion channels to open to allow
positive sodium ions to flow into the postsynaptic
cell.
This produces a depolarization of that cell
called an excitatory post-synaptic potential,
also known as the end-plate potential when
it occurs at the neuromuscular junction.
This depolarization leads to the opening of
voltage gated sodium channels, which causes
the end-plate potential to lead to an action
potential.
This action potential travels along the muscle
fiber and causes contraction of the muscle.
The enzyme acetylcholinesterase is also present
at the neuromuscular junction; it breaks down
acetylcholine and in the process terminates
its effects on the muscle fiber, thus ending
the communication between the motor neuron
and the muscle fiber.